I was searching for high ratio gearing to use in my DIY telescope drive
The first idea was a strain wave gearing, but 3D-printed wave is not reliable. I could use timing belt, but then gearing is noticeably bigger, and the belt has to much flexibility.
Finally, I created this: 3D-printed planetary compound, 354:1 ratio. Animation was done with Assembly3, Spreadsheet and a small python script. I uploaded everything on github.
There are two sets of ring gears:
-fixed, 60 teeth, module = 1
-moving, output, 59 teeth, module = 1.029
Planet gears are shared but modules of inside and outside teeth rows are different. Number of teeth in both is same.
I did not update the telescope repository yet, since gearing ratio will be changed probably. Also there are some teething issues (pun not intended) that have to be fixed, like too small output ring gear rigidity.
The new features in FreeCAD Link Branch were very useful. Eg. when I needed second very similar part but without holes, I could just suppress them instead of removing them. Supressing does not remove references, and does not break later features.
I used FCGear to external gears, because it has more features (like shift) than Part Desing Involute Gear. Unfortunately FCGear does not support internal gears, so I made them in Part Design.